Method of design based process control optimization

ABSTRACT

The present invention provides a method of design based process control optimization. In an embodiment, the method of design based process control optimization includes creating a circuit layout database including a design rule set. At least one algorithm is employed to query the circuit layout database to calculate at least one process specification limit. The method includes comparing the calculated at least one process specification limit with at least one predefined technology process tool capability to determine if the calculated at least one process specification limit allows for a manufacturable process. If the calculated at least one process specification limit does not allow for the manufacturable process, the limit may be re-optimized.

FIELD OF THE INVENTION

The present invention relates generally to the field of process controland more particularly to a method of design based process controloptimization.

BACKGROUND OF THE INVENTION

Process industries have developed various approaches to optimize orimprove manufacturing (e.g., reducing manufacturing costs whileimproving manufacturing yield) in efforts to remain competitive in anever increasing global economy. One approach has been to base processcontrol limits on estimated or historical process capabilities. Anadditional approach is to set control limits based on a set of designrules that represent the most aggressive requirements allowed on theprocess technology.

Although the present approaches have assisted the optimization ofprocess control, the approaches are limited under certain circumstances.First, basing process control limits on perceived tool or processcapabilities is disadvantageous for the tool or process capabilities maynot be sufficient to avoid yield loss or address reliability issues. Forexample, with such approach, process control limits often do not getmodified until problems are encountered in high volume production. Thus,such limitation may have significant financial impact on manufacturingincluding the inability to meet customer delivery schedules. Further,the approach of setting control limits based on a set of design rules isunfavorable because the derivation of the process specification limitsmay be extremely time-consuming for such process is typically performedmanually. In addition, adjustments for process exceptions that allowless or require more stringent requirements are also most oftenperformed manually and thus, may be time intensive. Moreover, suchadjustments are not usually made until either a yield or manufacturingconstraint is encountered.

Therefore, it would be desirable to provide a method of determining andoptimizing process control limits which allow the process control limitsto be modified sufficiently to reduce yield loss or reliability issues.

SUMMARY OF THE INVENTION

In an aspect of the present invention, a method of design based processcontrol optimization is provided. The method of design based processcontrol optimization may include creating a circuit layout databaseincluding a design rule set. At least one algorithm may be employed toquery the circuit layout database to calculate at least one processspecification limit. The method may also include comparing thecalculated at least one process specification limit with at least onepredefined technology process tool capability to determine if thecalculated at least one process specification limit allows for amanufacturable process. If the calculated process specification limitdoes not allow for the manufacturable process, the limit isre-optimized. For example, a re-optimization algorithm is employed tore-optimize all process inputs to maximize manufacturable capabilities.

In a further aspect of the present invention, a computer-readable mediumhaving computer-executable instructions for performing a method fordesign based process control optimization is provided. The method mayinclude creating a circuit layout database including a design rule set.In the present aspect, at least one algorithm may be employed to querythe circuit layout database to calculate at least one processspecification limit. The method may include comparing the calculated atleast one process specification limit with at least one predefinedtechnology process tool capability to determine if the calculatedprocess specification limit allows for a manufacturable process. If thecalculated at least one process specification limit does not allow for amanufacturable process, the at least one limit may be re-optimize.

In an additional aspect of the present invention, a method for designbased process control optimization is disclosed. The method may includecreating a design rule set. For example, the design rule set includes atleast one technology process requirement, manufacturing requirement ordesign for yield requirement. The method may include employing at leastone algorithm to query the design rule set to calculate at least oneprocess specification limit. The calculated at least one processspecification limit may be compared with the at least one technologyprocess requirement, manufacturing requirement, or design for yieldrequirement to determine if the at least one process specification limitcomplies with the at least one technology process requirement,manufacturing requirement, or design for yield requirement. If thecalculated at least one process specification limit does not comply withthe at least one technology process requirement, manufacturingrequirement, or design for yield requirement, the calculated at leastone process specification limit may be optimized.

It is to be understood that both the forgoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention as claimed. The accompanyingdrawings, which are incorporated in and constitute a part of thespecification, illustrate an embodiment of the invention and togetherwith the general description, serve to explain the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The numerous advantages of the present invention may be betterunderstood by those skilled in the art by reference to the accompanyingfigures in which:

FIG. 1 is a flow chart of a method of design based process controloptimization in accordance with an exemplary embodiment of the presentinvention;

FIG. 2 is a flow chart in accordance with an additional method of designbased process control optimization in accordance with an exemplaryembodiment of the present invention;

FIG. 3 is an example of a process specification limit optimization formanufacturability in accordance with an exemplary embodiment of thepresent invention;

FIG. 4 is an example of device specific process specification limitoptimization for manufacturability in accordance with an exemplaryembodiment of the present invention; and

FIG. 5 is an example of a process specification limit optimization fordesign yield in accordance with an exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the presently preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. It is to be appreciated that correspondingreference numbers refer to generally corresponding structures.

In general, a method of determining and optimizing process specificationlimits using software algorithms to minimize yield loss and maximizemanufacturability of the product is provided. The disclosed method isadvantageous for it includes automatic generation of processspecification limits for a technology node, re-optimization ofspecification limits to maximize manufacturability, automatic generationof product specific specification limits determined by actual designlayout which may vary from the technology specification limits, andidentification of process limit requirements that do not meet userdefined manufacturable requirements.

Referring to FIG. 1, a method 100 of design based process controloptimization is provided. In an exemplary embodiment, the method 100 ofdesign based process control optimization may include creating a circuitlayout database including a design rule set 102. For example, creating acircuit layout database 102 is constructed by use of software. In suchexample, the software adheres to the design rule set whereby the designrule set indicates allowable features such as an allowable featuredimension, an allowable feature spacing, an allowable feature density,and the like.

The method 100 may also include employing an algorithm to query thecircuit layout database to calculate at least one process specificationlimit 104. For example, the at least one algorithm is a softwarealgorithm. It is contemplated that additional algorithms may begenerated including one which may query the actual graphic data system(GDS) layout to determine process specification limits accordingly.

In the present embodiment, the method 100 includes comparing thecalculated at least one process specification limit with at least onepredefined technology process tool capability 106. For instance, the atleast one predefined technology process tool capability may include anestimated process tool capability, historical process tool capabilitiesand the like. In such instance, the calculated specification limits maybe compared to historical (or estimated) process tool capabilities todetermine if the calculated limits allow for a “manufacturable process.”In an embodiment, the manufacturable process is user defined and may bequantified by measurements such as Cpk>1.33 (Cpk being a measure of theactual process capability), rework rate<2%, scrap rate<0.5%, yield>90%,and the like.

In an exemplary embodiment, if the calculated at least one processspecification limit does not allow for the manufacturable process, thelimit may be re-optimized 108. Moreover, a re-optimization algorithm maybe employed to re-optimize all process inputs to maximize manufacturablecapabilities. In a further embodiment, the method 100 includesevaluating the at least one process specification limit to determine ifthe at least one process specification limit complies with a defineddesign for yield requirement 110.

Referring to FIG. 2, a method 200 for design based process controloptimization is disclosed. In an exemplary embodiment, the method 200includes creating a design rule set 202. For example, the design ruleset includes at least one technology process requirement, manufacturingrequirement or design for yield requirement. The method 200 may includeemploying at least one algorithm to query the design rule set tocalculate at least one process specification limit 204. The calculatedat least one process specification limit may be compared with the atleast one technology process requirement, manufacturing requirement, ordesign for yield requirement to determine if the at least one processspecification limit complies with the at least one technology processrequirement, manufacturing requirement, or design for yield requirement206. If the calculated at least one process specification limit does notcomply with the at least one technology process requirement,manufacturing requirement, or design for yield requirement, thecalculated at least one process specification limit may be optimized208.

Referring to FIG. 3, an example of employing the method 100 of designbased process control optimization in semiconductor manufacturing isprovided. In the present example, the technology process requirement isset so that the sum of Parameter A and Parameter B is less than 20.Further, the manufacturability requirement is set to a Cpk measurementof greater than 1.3. As illustrated in FIG. 3, the calculated processspecification limits for Rev1 meet the technology process requirements(i.e., sum of Parameter A and Parameter B are less than 20), but do notmeet the manufacturability requirement of Cpk>1.3 (i.e., Cpk B is lessthan 1.3). Through an optimization algorithm, the new processspecification limits for Rev2 meet both the technology processrequirements and the manufacturability requirements (both Cpk A and CpkB are >1.3). It is contemplated that the iterative process willhighlight process steps where weaknesses exist between the designrequirements and the manufacturing capabilities. Thus, in manyinstances, the iterative process is identifying the need for furtherprocess control improvements or hardware upgrades. It is contemplatedthat the iterative process may provide a more robust and cost effectiveprocess over prior art manufacturing methods for the present processallows a semiconductor manufacturer to quickly determine and implementprocess control limits that may ensure first pass success and does notrely upon costly yield excursions.

Referring to FIG. 4, an example of device specific process specificationlimit optimization for manufacturability in accordance with an exemplaryembodiment of the present invention is provided. The present exampleemploys similar parameters to those presented in FIG. 3 in which thetechnology process requirement is set so that the sum of Parameter A andParameter B is less than 20 and the manufacturability requirement is setto a Cpk measurement of greater than 1.3. However, a less stringentdevice specific process requirement is imputed which allows for widerspecification limits and possibly reduced manufacturing costs. Asillustrated in FIG. 4, the device specific process requirement is set sothat the sum of Parameter A and B is less than 25. Even with the relaxedprocess requirements, Rev1 output is not manufacturable whereby the CpKB value is not greater than 1.3. Therefore, the process specificationlimits are re-optimized and according to Rev2, the Cpk values for bothCpk A and Cpk B are greater than 1.3 and thus, such limits allow for amanufacturable process for the tested device.

In further exemplary embodiments, the disclosed invention is applied toa Design for Yield concept to search each device for special featuresthat require more stringent process conditions. For example, lessons mayhave been learned regarding very specific layout features that poseparticular manufacturing difficulties. One such example could be thatmetal lines spaced 0.4 um apart may be easily manufactured, however,metal posts with the same spacing result in electrical shorts that haveto be compensated for by changes to the process specification limits.This concept is illustrated in the example presented in FIG. 5.

Referring to FIG. 5, an example of a process specification limitoptimization for design yield in accordance with an exemplary embodimentof the present invention is provided. In the present example, thetechnology process requirement is set so that the sum of Parameter A andParameter B is less than 20 and the manufacturability requirement is setto a Cpk measurement of greater than 1.3. Further, the historical yieldloss process requirement or the Design for Yield requirement is set sothat Parameter B is less than 12. As illustrated in FIG. 5, Rev1 meetsthe technology process requirement and the Design for Yield requirement,but does not meet the manufacturability requirement. Re-Optimization ofSpec Limits in Rev2 meets process and manufacturability requirements,but fails the Design for Yield requirement (Parameter B is not less than12). Following a second re-optimization of the process specificationlimit outputs, the yielded specification limits are optimized tominimize yield loss and maximize manufacturability. However, theoriginal manufacturable requirement (Cpk>1.3) is not satisfied. The factthat Rev3 still does not meet the original manufacturable requirementCpk>1.3 highlights the need for further process control improvements forparameter B. As control improvements are made through process orhardware changes, the new process capabilities may be processed throughthe algorithms to re-optimize the process spec limits to further reducemanufacturing or yield loss costs.

It is contemplated that the disclosed method may also be used as amethod of “Advanced Process Control” that allows feed forward of processinformation from one step to the next. For example, the outputspecification results of one manufacturing process may be fed to othermanufacturing process steps downstream. The downstream process steps mayinclude requirements which may be changed in a manner that allows theoverall result to meet design requirements, thus avoiding a scrap event.It is further contemplated that the disclosed method may be applied toany industry where design tolerances have an impact on manufacturingspec limits.

It is to be noted that the foregoing described embodiments according tothe present invention may be conveniently implemented using conventionalgeneral purpose digital computers programmed according to the teachingsof the present specification, as may be apparent to those skilled in thecomputer art. Appropriate software coding may readily be prepared byskilled programmers based on the teachings of the present disclosure, asmay be apparent to those skilled in the software art.

It is to be understood that the present invention may be convenientlyimplemented in forms of a software package. Such a software package maybe a computer program product which employs a computer-readable storagemedium including stored computer code which is used to program acomputer to perform the disclosed function and process of the presentinvention. The computer-readable medium may include, but is not limitedto, any type of conventional floppy disk, optical disk, CD-ROM,magneto-optical disk, ROM, RAM, EPROM, EEPROM, magnetic or optical card,or any other suitable media for storing electronic instructions.

It is understood that the specific order or hierarchy of steps in theforegoing disclosed methods are examples of exemplary approaches. Basedupon design preferences, it is understood that the specific order orhierarchy of steps in the method can be rearranged while remainingwithin the scope of the present invention. The accompanying methodclaims present elements of the various steps in a sample order, and arenot meant to be limited to the specific order or hierarchy presented.

It is believed that the present invention and many of its attendantadvantages will be understood by the forgoing description. It is alsobelieved that it will be apparent that various changes may be made inthe form, construction and arrangement of the components thereof withoutdeparting from the scope and spirit of the invention or withoutsacrificing all of its material advantages. The form herein beforedescribed being merely an explanatory embodiment thereof. It is theintention of the following claims to encompass and include such changes.

1. A method for design based process control optimization, comprising:creating a circuit layout database including a design rule set; queryingthe circuit layout database to calculate at least one processspecification limit; comparing the calculated at least one processspecification limit with at least one predefined technology process toolcapability to determine if the at least one process specification limitallows for a manufacturable process; and recalculating the at least oneprocess specification limit, if the at least one process specificationlimit does not allow for the manufacturable process.
 2. The method asclaimed in claim 1, wherein the manufacturable process is user definedand may be quantified by measurements.
 3. The method as claimed in claim1, wherein the at least one predefined technology process toolcapability includes an estimated process tool capability.
 4. The methodas claimed in claim 1, wherein the method for design based processcontrol optimization is employed for semiconductor manufacturing.
 5. Themethod as claimed in claim 1, further comprising evaluating the at leastone process specification limit to determine if the at least one processspecification limit complies with a defined design for yieldrequirement.
 6. The method as claimed in claim 1, wherein the queryingof the circuit layout database includes at least one algorithm.
 7. Themethod as claimed in claim 1, wherein the creating a circuit layoutdatabase is constructed by use of software.
 8. The method as claimed inclaim 7, wherein the software adheres to the design rule set, the designrule set indicating at least one of an allowable feature dimension, anallowable feature spacing, or an allowable feature density.
 9. Acomputer-readable medium having computer-executable instructions forperforming a method for design based process control optimization, themethod comprising: creating a circuit layout database including a designrule set; querying the circuit layout database to calculate at least oneprocess specification limit; comparing the calculated at least oneprocess specification limit with at least one predefined technologyprocess tool capability to determine if the at least one processspecification limit allows for a manufacturable process; andrecalculating the at least one process specification limit, if the atleast one process specification limit does not allow for themanufacturable process.
 10. The computer-readable medium as claimed inclaim 9, wherein the manufacturable process is user defined and may bequantified by measurements.
 11. The computer-readable medium as claimedin claim 9, wherein the at least one predefined technology process toolcapability includes an estimated process tool capability.
 12. Thecomputer-readable medium as claimed in claim 9, wherein the method ofthe querying of the circuit layout database includes at least onealgorithm.
 13. The computer-readable medium as claimed in claim 9,wherein the method for design based process control optimization isemployed for semiconductor manufacturing.
 14. The computer-readablemedium as claimed in claim 9, wherein the method further comprisesevaluating the at least one process specification limit to determine ifthe at least one process specification limit complies with a defineddesign for yield requirement.
 15. The computer-readable medium asclaimed in claim 9, wherein the design rule set indicates at least oneof an allowable feature dimension, an allowable feature spacing, or anallowable feature density.
 16. A method for design based process controloptimization, comprising: creating a design rule set, the design ruleset including at least one technology process requirement, manufacturingrequirement or design for yield requirement; employing at least onealgorithm to query the design rule set to calculate at least one processspecification limit; comparing the at least one process specificationlimit with the at least one technology process requirement,manufacturing requirement, or design for yield requirement to determineif the at least one process specification limit complies with the atleast one technology process requirement, manufacturing requirement, ordesign for yield requirement; and recalculating the at least one processspecification limit, if the at least one process specification limitdoes not comply with the at least one technology process requirement,manufacturing requirement, or design for yield requirement.
 17. Themethod for design based process control optimization as claimed in claim16, wherein the design rule set includes at least one device specificprocess requirement.
 18. The method for design based process controloptimization as claimed in 17, further comprising comparing the at leastone process specification limit with the at least one device specificprocess requirement.
 19. The method for design based process controloptimization as claimed in claim 16, wherein the method for design basedprocess control optimization is employed for semiconductormanufacturing.